Two Invercargill houses were blazing within hours of each other last night, with no one injured in either case.

Fire and Emergency New Zealand shift manager Lyn Crosson said two fire appliances were called after 8pm to the first house fire on Rosewood Drive.

She said the fire was "well ablaze" and required an additional two appliances to extinguish the fire, which originated in the connected garage. 

The fire was deemed suspicious and an investigator, who was on the scene last night, would return later today to investigate further. 

No-one was in the house, she said. 

Just before 10pm, fire services were called to a second house fire on William Street, also requiring four engines in total.

While she did not know the source of this fire, it was not deemed suspicious, and the occupants of the house got out with no injuries. 

"They both suffered substantial damage from the fires, but the second house on William Street would have been more damaged than the [one on] Rosewood Drive."

While not deemed suspicious, a fire investigator would also be returning to the site today in order to determine the cause.